Do I need interleaving

[D-Dan]

Since I migrated from Orange/Wanadoo/Freeserve or whoever the hell they are in Oct '06 I've generally been pleased as punch with my IDNet service. Some of you will be aware of recent problems I've had (down to BT as far as I can tell), and my SNR seems to be targeted somewhat high now. I've just emailed IDNet about this.

Since migration, I've been on an interleaved connection. I've asked IDNet to ask BT to lower my target SNR to around 8 (I was previously stable at 6 and below - but let's not tempt the BB gods), and I'm thinking of asking for interleaving to be turned off too. I've included a request for an opinion in my mail to IDNet, but opinions here would be welcome too.

Steve

[RA-1972]

This might help higher the snr the better if i can read .

The SNR margin and Attenuation values should be reasonable - for
example:
SNR margin (higher the better) : 25-30dB is normal, below 6dB is a
real problem.
Line Attenuation (lower the better) : 10-20 is normal, above 40 is a
real problem.

[D-Dan]

Well - I've been quite happy with SNR 6 (and lower) with Attenuation of 45 for a year. I'm thinking - aim for a higher SNR, and can I afford to turn interleaving off.

My router will hang on to it's nuts at low SNR as a general rule (and on my backup netgear - I regularly saw sub zero SNR - though I believe that's simply because it doesn't read the SNR very well).

My question is, if I take a higher target SNR, can I afford to have interleaving turned off? I'm thinking it may buy me a few Kbs.

Edit:

And since when was a D/L SNR of 20-30 normal - that's very high.

[Simon]

All the right people to ask seem to have scuttled off for now, Steve, but I'm sure they'll soon be lured back. 

[Ann]

I got IDNet to ask BT to lower my noise margin and they also turned off interleaving.  For two days I had a synch speed of 8128 but then it was suddenly all back on again.. interleaving on and a noise margin of 15 with a synch speed of 6336.  It seems my line is deteriorating as it used to be stable but I'm glad we tried it.  If the line isn't good enough you will soon know.

[Steve]

If your SNR margin has been raised and interleave turned on.This is an attempt by BT to stabilise your connection and improve error performance. Therefore if you have your SNR margin reduced and interleave turned off  you may achieve a higher sync but you may reduce throughput due to errors and the need to re transmit data.I suppose you need to look at possible ways of improving your connection and I am sure people with far greater knowledge than myself will give you good advice soon.

[Sebby]

With regards to your SNRM, you can't have BT set your target SNRM to 8dB; it can only be 6, 9, 12, or 15. You may indeed see figures in between these, and that's because the SNRM has moved since the router sync'd at the target figure. Generally, BT won't adjust it manually, either. Their view is that if the DLM has adjusted the target SNRM, the line isn't stable, and usually (not always} this is correct.

I know you've had stability problems, Steve, and you don't sync very high, so this suggests a less-than-perfect line. Generally speaking, you need a very good line to not require interleaving. Having it switched off really can do more harm than good in most cases. My suggestion would be to leave interleaving on.

[D-Dan]

Thanks Sebby  your explanation makes a lot of  sense - apart from the SNRM bit

Given that I've been stable for over a year before - and two weeks since my problems - I guess my sync was down to external factors beyond my control and now fixed. So at least - I want my target SNR reduced - right?

[Rik]

It will do no harm to get the target NM reduced, Steve. If the line can't handle it, it will be pushed back up again. However... BT can be reluctant to reduce it if it was set by the DLM software and there hasn't been a fault which they have resolved. IDNet will do their best for you, but sometimes BT won't budge.